I'm a pretty big fan of The Beach Boys and yet - I had no idea they backed Annette Funicello for the title track of Disney's The Monkey's Uncle in 1965.
And yet - here they are - the classic lineup including Brian Wilson (who was probably working on Pet Sounds around the same time he agreed to do this). At this point, I believe Brian stopped performing live - and was usually replaced by Bruce Johnston. So we should all consider ourselves lucky.
"Monkey's Uncle" by the way, was later covered - capably, I might add - by Dev2.0, the all-children's Devo cover band. Would that there was a YouTube of that.